The Bio-Block uses microalgae that perform photosynthesis and produce calcium carbonate — the same material as coral reefs — transforming CO₂ into zero-carbon blocks
In nature, coral reefs take decades to produce calcium carbonate — the mineral that forms their rigid structures — using only sunlight and CO₂ dissolved in seawater.
Additionally, scientists from the American startup Prometheus Materials and the architecture firm SOM have discovered how to replicate this process in a laboratory using microalgae — and transform the result into building blocks.
Consequently, the Bio-Block is a building block that literally grows: the algae perform photosynthesis inside bioreactors, absorb CO₂ from the air, and produce the mineral that forms the base of the material.
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In practice, instead of burning limestone at 1,450°C in industrial kilns — as the conventional cement industry does — the algae do the same work at room temperature, consuming CO₂ instead of emitting it.
3 times stronger and 15% lighter than concrete
Laboratory tests revealed surprising results. In fact, the Bio-Block achieves compressive strength 3 times greater than conventional concrete.
Additionally, the material is 15 to 20% lighter and has sound absorption capacity 12 times better than traditional concrete.

How algae transform CO₂ into building material
The process begins in bioreactors — transparent tanks where microalgae are cultivated with water, sunlight, and CO₂.
Consequently, during photosynthesis, the algae absorb CO₂ and convert it into calcium carbonate — the same mineral that forms shells, pearls, and coral reefs.
Then, this biogenic material is harvested, mixed with aggregates, and molded into blocks — without the need for kilns, without burning fossil fuels.
To get an idea of the scale of the impact: the cement industry is responsible for 8% of all global CO₂ emissions. Additionally, if the Bio-Block replaced conventional cement on a large scale, it would prevent about 2 gigatons of CO₂ per year.
- Base material: calcium carbonate produced by microalgae via photosynthesis
- Strength: 3x stronger than conventional concrete
- Weight: 15-20% lighter
- Sound absorption: 12x better
- Carbon: zero emission (sequesters CO₂ during production)
- Potential: cut 8% of global emissions if used on a large scale

From university to real construction
Prometheus Materials was born from a research program at the University of Colorado Boulder. Thus, the partnership with SOM — one of the largest architecture firms in the world — accelerated the transition from the laboratory to real applications.
Additionally, the company plans to launch a ready-mix concrete recipe that will allow building towers above 3 or 4 stories — overcoming the current limitation of masonry blocks.
However, challenges remain. Production on a large scale still depends on bioreactor infrastructure and the cost per unit is higher than traditional concrete. However, with carbon pricing becoming a reality in more and more countries, the equation could quickly reverse.

Even so, the fact that a building block can grow with sunlight, absorb CO₂ and be stronger than concrete sounds almost too good to be true. But the tests are there — and the first building material that literally breathes is already a reality.

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